High frequency response servo valve

ABSTRACT

Metering means for hydraulic fluid including a metering sleeve and a spool valve within the sleeve movable to meter fluid through the sleeve in accordance with the position of diaphragm springs engaged therewith at the opposite ends thereof, a voice coil connected to one of the diaphragm springs and means for creating a permanent magnetic field about the coil whereby high frequency movement of the voice coil and therefore the spool valve is effected by varying the electric signal in the coil.

United States Patent 1191 Sallberg et al.

HIGH FREQUENCY RESPONSE SERVO VALVE Inventors: David W. Sallbergjarrning t ori;

Peter 1. Clark, Troy; Wesley R. Parker; Robert D. Nicholson, both ofBirmingham. all of Mich.

Assignee: Koehring Company, Milwaukee,

Wis.

Filed: Apr. 8, 1971 Appl. No.2 132,276

US. Cl. 137/625.6l, l37/625.65 Int. Cl. Fl6k 31/10, F15b 11/08 Field ofSearch 137/625.65, 596.17,

References Cited UNITED STATES PATENTS 7/1969 Andrews 137/625.61 9/1969Boonshaft et aI 137/625.65 X 12/1951 Best 251/137 X 9/1960 Reen etal.....

1451 July31,1973

3,099,230 7 1963 Holzbock 137/83 3,001,549 9/1961 Nelson et a1...137/625.27 2,582,088 1/1952 Walthers 137 501 x 2.669247 2/ 1954 Olah137/84 FOREIGN PATENTS OR APPLICATIONS 196,517 6/1965 Sweden l37/625.641,197,897 7 1970 Great Britain 137/625.65

Primary Examiner-Henry T. Klinksiek Assistant Examiner-Robert J. MillerAttorney-Whittemore, I-Iulbert & Belknap [5 7 ABSTRACT 11 Claims, 3Drawing Figures 52 54 12 Z 10 f 1 28 us 2s 4s f 88 g g 120 5s fig; 1 221043 24 122 1' so 102 94 r 32 7o} '72 18 I 76 I 46 I HIGH FREQUENCYRESPONSE SERVO VALVE BACKGROUND OF THE INVENTION 1. Field of theInvention The invention relates to electrohydraulic servo valves andrefers more specifically to a high frequency responsive electrohydraulicservo valve of the spool type wherein a voice coil movable in apermanent magnetic field is the motor means.

2. Description of the Prior Art In the past, electrohydraulic servovalves have often included a metering spool carrying centrally locatedopposed jets and a flapper valve positioned between the jets causingmovement of the metering spool in accordance with the position of theflapper valve with respect to the jets. With such valves the motor meanshas usually been an electromagnet operable on the end of the flappervalve opposite the jets for pivoting the flapper valve about a pivotpoint produced by a torsion tube or the like. With such valve structurethe frequency of response is limited due to the physical characteristicsof the motor means, flapper valve and pivot structure and the responseof the metering spool to the variation in pressures at the jets. Highfrequency response of such valves is not to be expected.

SUMMARY OF THE INVENTION In accordance with the invention, a highfrequency response electrohydraulic servo valve is provided comprisingmetering'means including a metering sleeve and a spool valve movableaxially within the sleeve, means for positioning the spool valve axiallyincluding a diaphragm spring at each end of the spool and engagedtherewith, an adjustment screw between at least one diaphragm spring andthe spool, and motor means for moving one of the diaphragm springs andtherefore the spool at a relatively high frequency including a voicecoil connected to the one diaphragm spring and means for producing apermanent magnetic field about the voice coil.

The diaphragm springs have openings extending therethrough and the motormeans includes openings therethrough whereby the hydraulic pressures areequalized on the opposite sides of the diaphragm springs and in themotor means to facilitate the high frequency operation and provide asubstantially completely wet electrohydraulic servo valve.

BRIEF DESCRIPTION OF THE DRAWINGS F IG. 1 is a longitudinal section viewof an electrohydraulic servo valve constructed in accordance with theinvention and taken substantially on the line ll in FIG. 2.

FIG. 2 is a cross section view of the electrohydraulic servo valveillustrated in FIG. I taken substantially on the line 22 in FIG. 1.

FIG. 3 is a partial cross section view of the electrohydraulic servovalve illustrated in FIG. 1 taken substantially on the line 3-3 in FIG.1.

DESCRIPTION OF THE PREFERRED EMBODIMENT The electrohydraulic servo valveas illustrated in FIGS. 1-3 includes the metering means 12 includingmetering sleeve 14 and metering spool 16 therein. Resilient diaphragmmeans 18 and 20 are provided at the opposite ends of the metering spool16 for maintaining the metering spool 16 in a predetermined adjustedposition within the sleeve 14. Motor means 22 is connected to theresilient means 20 for moving the metering spool 16 at a high frequencyin accordance with an electrical signal passed through the voice coil 24of the motor means.

More specifically, the metering means 12 includes a valve body 28 havinga central passage 30 extending therethrough with metering annuluses 32therein. Passages 34 and 36 extend transversely through the valve body28 and may be connected directly to a member such as a hydrauliccylinder (not shown) which it is desired to actuate in accordance withthe fluid flow through the valve 10. Hydraulic fluid enters the valve 10through the passage 38 therein and leaves the valve 10 to a sump or thelike through the passages 40 and 42. Additional passages 44 and 46 areprovided in the valve body 28 which are returned to the hydraulic fluidsupply which may be the same supply to which the passage 42 is connectedwhereby the hydraulic pressure at the opposite ends of the valve 10 isequalized. Annular recesses 48 and 50 are provided at the opposite endsof the body 28 to receive the resilient diaphragm means 18 and 20.

The metering means 12 further includes the end plate 52 secured to theend 54 of the body 28 by convenient means such as bolts 56 or the like.Plug 58 is provided in the end plate 52 and may be removed in use topermit adjustment of the adjusting screw 60 carried by the resilientdiaphragm means 18.

The metering sleeve 14 is securely held in the passage 30 in the bodymember 28 by means of the annular nuts 62 and 64 at the opposite endsthereof. The metering sleeve 14, as shown, has annular sealing lands 66thereon between which annular metering grooves 68 are provided inalignment with the metering annuluses 32 in the body 28. Transverseopenings 70, 711, 72, 73 and 74 are provided in the metering sleeve tometer fluid therethrough in conjunction with the metering spool 16.

Metering spool 16, as shown, has the three metering lands 76, 78 and 80thereon which are operable in conjunction with the metering sleeve 14 tometer fluid through the passages 34, 36, 38 and 42 of the body 28.

Thus, on movement of the metering spool 16 to the left as shown in FIG.1, hydraulic fluid will be metered through passage 38, passage 74 andpassage 72 into the passage 36. At the same time, hydraulic fluid willbe metered from the passage 34 through the passage 70, out through thepassage 71 and through passage 40, passage 73 and passage 42. Onmovement of the spool valve 16 to the right, fluid is passed from thepassage 38 into the passage 34 and at the same time hydraulic fluid ispassed out through the passage 36 and passage 42.

The resilient diaphragm means 18 includes a diaphragm spring 86 which issecured around the periphery thereof in the recess 48 in body 28 by theannular nut 88. The diaphragm spring 86 has a central opening 90extending therethrough through which the boss 92 extends. Boss 92 issecured to the diaphragm spring 86 by nut 94. The adjusting screw 60 isthreaded through the boss 92. Both the adjusting screw 60 and theadjacent end of the metering spool 16 are provided with a conical recesstherein to receive the conical ends of the force transfer member 96. Asshown best in FIG. 2, the diaphragm spring 86 has openings 98therethrough to equalize the pressure on the opposite sides of thediaphragm spring 86.

The resilient means at the opposite end of the metering spool 16 is thesame as the resilient means 18, with the exception of the adjustingscrew 60 which is not present in the resilient means 20. lnstead of theadjusting screw 60, a screw 100 extends through the boss of theresilient means 20 to which the trough 102 of the motor means 26 issecured by nut 106.

The motor means 22 includes the voice coil 24 carried by trough 102which, as shown best in FIG. 3, has openings 108 therethrough toequalize the pressure on the opposite sides thereof. The permanentmagnetic field of the motor means 22 is provided by the cylindricalpermanent magnet 26. The permanent magnetic field from the magnet 26 isdirected through the voice coil 24 by means of the soft magneticmaterial members 110 and 112 positioned as shown. The permanent magnet26 and the members 110 and 112 are maintained in a predeterminedposition by the motor means cover plate 114 which may be secured to thebody member 28 by convenient means such as bolts (not shown) inconjunction with the spacers 116 and 118 and the annular spring 120.

In operation, the voice coil 24 is movable relative to the members 110and 112 in accordance with the electrical signal passed therethrough,since movement of the coil will be produced in accordance with theelectrical signal in the voice coil and the magnetic field provided bythe permanent magnet 26. Openings 122 and 124 are provided in the member110 to permit equalizing of the pressure in the space 126 between themembers 110 and 112 and the permanent magnet 26.

In operation of the high frequency response electrohydraulic servovalve, a hydraulic fluid input under pressure is connected to thepassage 38, the passages 34 and 36 are connected to a device it isdesired to actuate in accordance with a high frequency electricalsignal, and the passages 42 and 46 are connected to the return line ofthe source of hydraulic fluid under pressure. The opposite ends of thevoice coil 24 are connected to a source of high frequency electricalenergy. The initial position of the metering spool 16 is adjusted bymeans of the adjusting screw 60.

Due to the high frequency electrical signal, the voice coil 24 is causedto move axially of the metering spool 16 at a corresponding frequency.Movement of the voice coil 24 causes movement of the resilient diaphragmspring in the resilient means 20 so that the metering spool 16 is movedsimilarly due to the force transfer members between the resilient means18 and 20 and the metering spool 16. Since the pressure on the oppositesides of the resilient means 18 and 20 and the pressure on the oppositesides of the voice coil 24 are all equalized, rapid response of themetering spool 16 to a high frequency electrical signal which may be programmed or varied as desired is providedv While one embodiment of thepresent invention has been described in detail. it will be understoodthat other embodiments and modifications thereof are contemplated. It isthe intention to include all modifications and embodiments of theinvention as are defined by the appended claims within the scope of theinvention.

What I claim as my invention is:

1. An electrohydraulic servo valve comprising a valve body having anelongated opening therethrough and including passages extending thereintransversely of the opening therethrough through which hydraulic fluidis metered, a metering sleeve positioned within the opening through thevalve body member having transverse openings therein through whichhydraulic fluid is metered into and out of the passages, an elongatedspool valve positioned within the metering sleeve for axial movementtherein to meter the hydraulic fluid through the openings in the sleeveinto and out of the passages, diaphragm biasing means positioned overthe opposite ends of the opening through the valve body and supported bythe valve body, separate force transfer members positioned between eachdiaphragm biasing means and a corresponding end of the spool valvewithout being connected to either the spool valve or biasing means totransfer only compressive forces therein between the spool and biasingmeans for moving the spool valve within the metering sleeve inaccordance with the movement of the diaphragm biasing means, means foradjusting the initial compressive forces in the force transfer members,a voice coil secured to at least one of the diaphragm biasing means formovement therewith, permanent magnet means carried by the valve bodypositioned adjacent the voice coil for causing movement of the voicecoil in accordance with an electrical signal passed through the voicecoil, and means for equalizing the hydraulic pressure on both sides ofthe diaphragm biasing means and the voice coil.

2. Structure as set forth in claim 1 wherein the diaphragm biasing meansare perforate to provide passage of hydraulic fluid therethrough andmeans are provided in the valve body for connecting the hydraulic fluidadjacent both of the diaphragm biasing means.

3. Structure as set forth in claim 1 wherein the permanent magnet meansincludes a cylindrical permanent magnet positioned concentrically of andpositioned axially and radially outwardly of the voice coil, a soft ironcore having a T-shaped longitudinal cross section the stem of which ispositioned within the voice coil and the crossbar of which is engagedwith one end of the cylindrical permanent magnet and a cylindrical soft'iron member positioned radially outwardly of and concentric with thevoice coil one end of which is in engagement with the other end of thecylindrical pennanent magnet whereby the soft iron members and thecylindrical permanent magnet define a cylindrical chamber at one end ofthe voice coil, and passages in the stern of the one soft iron coreproviding communication between the other end of the voice coil and thecylindrical chamber at the one end of the voice coil whereby hydraulicfluid pressure is equalized on both ends of the voice coil.

4. Structure as set forth in claim 1 wherein the means for adjusting theinitial compressive forces in the force transfer members comprises anadjusting screw carried by each of the diaphragm biasing means centrallythereof in engagement with the separate force transfer members.

5. An electrohydraulic servo valve comprising a valve body having anelongated opening therethrough and including passages thereintransversely of the opening therethrough through which hydraulic fluidis metered, an elongated spool valve positioned within the opening foraxial movement therein to meter the hydraulic fluid through the openingin the valve body into and out of the passages, diaphragm biasing meanspositioned over the opposite ends of the opening through the valve bodyand supported by the valve body, separate force transfer memberspositioned between each diaphragm biasing means and a corresponding endof the spool valve without being connected to either the spool valve ordiaphragm biasing means to transfer only compressive forces thereinbetween the spool valve and diaphragm biasing means for moving the spoolvalve within the opening in accordance with the movement of thediaphragm biasing means, means carried by the diaphragm biasing meansand operable between the diaphragm biasing means and force transfermembers for adjusting the initial bias between the diaphragm biasingmeans and spool valve, a voice coil secured to at least one of thediaphragm biasing means for movement therewith, permanent magnet meanscarried by the valve body positioned adjacent the voice coil for causingmovement of the voice coil in accordance with an electrical signalpassed through the voice coil, and means operably associated with thediaphragm biasing means and voice coil for equalizing the hydraulicpressure on both sides of the diaphragm biasing means and the voicecoil. 7

6. Structure as set forth in claim 5, wherein the means for equalizingthe hydraulic pressure on both sides of the diaphragm biasing meansincludes openings through the diaphragm biasing means and a passage inthe valve body member for connecting hydraulic fluid adjacent both ofthe diaphragm biasing means.

7. Structure as set forth in claim 5, wherein the permanent magnet meansincludes a cylindrical permanent magnet positioned concentrically of andboth axi ally and radially outwardly of the voice coil with respect tothe spool valve, a soft iron core having a T- shaped longitudinal crosssection the stem of which is positioned within the voice coil and thecross bar of which is engaged with one end of the cylindrical permanentmagnet and a cylindrical soft iron member positioned radially outwardlyof and concentric with the voice coil one end of which is in engagementwith the other end of the cylindrical permanent magnet whereby the softiron members and the cylindrical permanent magnet define a cylindricalchamber at one end of the voice coil and wherein the means forequalizing the hydraulic pressure on both sides of the voice coilincludes passages in the stern of the one soft iron core providingcommunication between the other end of the voice coil and thecylindrical chamber at the one end of the voice coil.

8. Structure as set forth in claim 5, wherein the means for adjustingthe initial bias between the spool valve and the diaphragm biasing meanscomprises adjusting screws carried by the diaphragm biasing meanscentrally thereof for movement transversely of the diaphragm biasingmeans in engagement with the ends of the force transfer members.

9. Structure as set forth in claim 8 and further including an opening inthe valve body member adjacent one adjusting screw and plug meansthreadedly secured within the opening whereby the bias between thediaphragm biasing means and the spool may be adjusted on removal of theplug without further disassembly of the electrohydraulic servo valve.

10. An electrohydraulic servo valve comprising a cylindrical valve bodymember, a cylindrical opening extending axially through the valve bodymember, transverse passages passing through the valve body member incommunication with the axial opening therethrough, a metering sleevepositioned in the opening for metering fluid between the transversepassages, a spool valve positioned within the metering sleeve forreciprocation therein to meter fluid into and out of the passagesthrough the metering sleeve, circular perforate diaphragm biasing meanssecured to the opposite ends of the valve body member over the openingtherein, a passage in the valve body member connecting the areassurrounding the diaphragm biasing means for equalizing hydraulic fluidpressure therein, an adjusting screw threadably received centrally ofone of the biasing diaphragms, a second adjusting screw and a voice coilthreadably received in and carried centrally of the other of saidbiasing diaphragms, separate force transfer members positioned betweenthe opposite ends of the spool valve and the associated adjusting screwswhich are not secured to either the spool valve or adjusting screws soas to transfer only compressive forces therein between the biasingdiaphragms and spool valve whereby the bias on the spool valve may beadjusted on adjustment of the adjusting screws, a valve body cappositioned over one end of the valve body member adjacent the onebiasing diaphragm, and permanent magnet motor means positioned over theother end of the valve body member operably associated with the voicecoil for movement of the voice coil and thus the spool valve inaccordance with the electrical energy passed through the voice coil.

11. Structure as set forth in claim 10 wherein the permanent magnetmotor means includes a cylindrical permanent magnet positionedconcentrically of and both axially and radially outwardly of the voicecoil with respect to the spool valve, a soft iron core having a T-shaped longitudinal cross section the stem of which is positioned withinthe voice coil and the crossbar of which is engaged with one end of thecylindrical permanent magnet and a cylindrical soft iron memberpositioned radially outwardly and concentrically of the voice coil oneend of which is in engagement with the other end of the cylindricalpermanent magnet whereby the soft iron members and the cylindricalpermanent magnet define a cylindrical chamber at one end of the voicecoil, and passages in the stem of the one soft iron core providingcommunication between the other end of the voice coil and thecylindrical chamber at the one end of the voice coil whereby hydraulicfluid pressure is equalized on both ends of the voice coil.

* t I I

1. An electrohydraulic servo valve comprising a valve body having anelongated opening therethrough and including passages extending thereintransversely of the opening therethrough through which hydraulic fluidis metered, a metering sleeve positioned within the opening through thevalve body member having transverse openings therein through whichhydraulic fluid is metered into and out of the passages, an elongatedspool valve positioned within the metering sleeve for axial movementtherein to meter the hydraulic fluid through the openings in the sleeveinto and out of the passages, diaphragm biasing means positioned overthe opposite ends of the opening through the valve body and supported bythe valve body, separate force transfer members positioned between eachdiaphragm biasing means and a corresponding end of the spool valvewithout being connected to either the spOol valve or biasing means totransfer only compressive forces therein between the spool and biasingmeans for moving the spool valve within the metering sleeve inaccordance with the movement of the diaphragm biasing means, means foradjusting the initial compressive forces in the force transfer members,a voice coil secured to at least one of the diaphragm biasing means formovement therewith, permanent magnet means carried by the valve bodypositioned adjacent the voice coil for causing movement of the voicecoil in accordance with an electrical signal passed through the voicecoil, and means for equalizing the hydraulic pressure on both sides ofthe diaphragm biasing means and the voice coil.
 2. Structure as setforth in claim 1 wherein the diaphragm biasing means are perforate toprovide passage of hydraulic fluid therethrough and means are providedin the valve body for connecting the hydraulic fluid adjacent both ofthe diaphragm biasing means.
 3. Structure as set forth in claim 1wherein the permanent magnet means includes a cylindrical permanentmagnet positioned concentrically of and positioned axially and radiallyoutwardly of the voice coil, a soft iron core having a T-shapedlongitudinal cross section the stem of which is positioned within thevoice coil and the crossbar of which is engaged with one end of thecylindrical permanent magnet and a cylindrical soft iron memberpositioned radially outwardly of and concentric with the voice coil oneend of which is in engagement with the other end of the cylindricalpermanent magnet whereby the soft iron members and the cylindricalpermanent magnet define a cylindrical chamber at one end of the voicecoil, and passages in the stem of the one soft iron core providingcommunication between the other end of the voice coil and thecylindrical chamber at the one end of the voice coil whereby hydraulicfluid pressure is equalized on both ends of the voice coil.
 4. Structureas set forth in claim 1 wherein the means for adjusting the initialcompressive forces in the force transfer members comprises an adjustingscrew carried by each of the diaphragm biasing means centrally thereofin engagement with the separate force transfer members.
 5. Anelectrohydraulic servo valve comprising a valve body having an elongatedopening therethrough and including passages therein transversely of theopening therethrough through which hydraulic fluid is metered, anelongated spool valve positioned within the opening for axial movementtherein to meter the hydraulic fluid through the opening in the valvebody into and out of the passages, diaphragm biasing means positionedover the opposite ends of the opening through the valve body andsupported by the valve body, separate force transfer members positionedbetween each diaphragm biasing means and a corresponding end of thespool valve without being connected to either the spool valve ordiaphragm biasing means to transfer only compressive forces thereinbetween the spool valve and diaphragm biasing means for moving the spoolvalve within the opening in accordance with the movement of thediaphragm biasing means, means carried by the diaphragm biasing meansand operable between the diaphragm biasing means and force transfermembers for adjusting the initial bias between the diaphragm biasingmeans and spool valve, a voice coil secured to at least one of thediaphragm biasing means for movement therewith, permanent magnet meanscarried by the valve body positioned adjacent the voice coil for causingmovement of the voice coil in accordance with an electrical signalpassed through the voice coil, and means operably associated with thediaphragm biasing means and voice coil for equalizing the hydraulicpressure on both sides of the diaphragm biasing means and the voicecoil.
 6. Structure as set forth in claim 5, wherein the means forequalizing the hydraulic pressure on both sides of the diaphragm biasingmeans includes openings through the diaphragm biasing means and apassage in the valve body member for connecting hydraulic fluid adjacentboth of the diaphragm biasing means.
 7. Structure as set forth in claim5, wherein the permanent magnet means includes a cylindrical permanentmagnet positioned concentrically of and both axially and radiallyoutwardly of the voice coil with respect to the spool valve, a soft ironcore having a T-shaped longitudinal cross section the stem of which ispositioned within the voice coil and the cross bar of which is engagedwith one end of the cylindrical permanent magnet and a cylindrical softiron member positioned radially outwardly of and concentric with thevoice coil one end of which is in engagement with the other end of thecylindrical permanent magnet whereby the soft iron members and thecylindrical permanent magnet define a cylindrical chamber at one end ofthe voice coil and wherein the means for equalizing the hydraulicpressure on both sides of the voice coil includes passages in the stemof the one soft iron core providing communication between the other endof the voice coil and the cylindrical chamber at the one end of thevoice coil.
 8. Structure as set forth in claim 5, wherein the means foradjusting the initial bias between the spool valve and the diaphragmbiasing means comprises adjusting screws carried by the diaphragmbiasing means centrally thereof for movement transversely of thediaphragm biasing means in engagement with the ends of the forcetransfer members.
 9. Structure as set forth in claim 8 and furtherincluding an opening in the valve body member adjacent one adjustingscrew and plug means threadedly secured within the opening whereby thebias between the diaphragm biasing means and the spool may be adjustedon removal of the plug without further disassembly of theelectrohydraulic servo valve.
 10. An electrohydraulic servo valvecomprising a cylindrical valve body member, a cylindrical openingextending axially through the valve body member, transverse passagespassing through the valve body member in communication with the axialopening therethrough, a metering sleeve positioned in the opening formetering fluid between the transverse passages, a spool valve positionedwithin the metering sleeve for reciprocation therein to meter fluid intoand out of the passages through the metering sleeve, circular perforatediaphragm biasing means secured to the opposite ends of the valve bodymember over the opening therein, a passage in the valve body memberconnecting the areas surrounding the diaphragm biasing means forequalizing hydraulic fluid pressure therein, an adjusting screwthreadably received centrally of one of the biasing diaphragms, a secondadjusting screw and a voice coil threadably received in and carriedcentrally of the other of said biasing diaphragms, separate forcetransfer members positioned between the opposite ends of the spool valveand the associated adjusting screws which are not secured to either thespool valve or adjusting screws so as to transfer only compressiveforces therein between the biasing diaphragms and spool valve wherebythe bias on the spool valve may be adjusted on adjustment of theadjusting screws, a valve body cap positioned over one end of the valvebody member adjacent the one biasing diaphragm, and permanent magnetmotor means positioned over the other end of the valve body memberoperably associated with the voice coil for movement of the voice coiland thus the spool valve in accordance with the electrical energy passedthrough the voice coil.
 11. Structure as set forth in claim 10 whereinthe permanent magnet motor means includes a cylindrical permanent magnetpositioned concentrically of and both axially and radially outwardly ofthe voice coil with respect to the spool valve, a soft iron core havinga T-shaped longitudinal cross section the stem of which is positionedwithin the voice coil and the crossbar of which is engaged with one endof the cylindrical permanent magnet and a cylindrical soft iron memberpositIoned radially outwardly and concentrically of the voice coil oneend of which is in engagement with the other end of the cylindricalpermanent magnet whereby the soft iron members and the cylindricalpermanent magnet define a cylindrical chamber at one end of the voicecoil, and passages in the stem of the one soft iron core providingcommunication between the other end of the voice coil and thecylindrical chamber at the one end of the voice coil whereby hydraulicfluid pressure is equalized on both ends of the voice coil.